1. Field of the Invention
The present invention relates to a mobile communication system for providing contents to a mobile communication terminal, and more particularly to the mobile communication system suitable to provide contents to the mobile communication terminal which moves in a wide area, and a mobile communication method and a mobile communication program used in the mobile communication system.
The present application claims priority of Japanese Patent Application No. 2000-096337 filed on Mar. 31, 2000, which is hereby incorporated by reference.
2. Description of Related Art
As an integration technique, a packaging technique, a communication technique and a like advance, it is possible for a mobile user terminal as a mobile communication terminal having a radio communication function, such as a cellular telephone to access various servers in the Internet in which computer networks are connected one another. As a result, a user of the mobile user terminal can not only transmit and receive an electronic mail but also browse information such as characters and images of content data obtained from various servers using a display section of the mobile user terminal.
FIG. 7 is a diagram showing a configuration of a mobile communication system for browsing contents in the Internet using a mobile user terminal 10. When the mobile user terminal 10 is a cellular telephone, the mobile user terminal (cellular telephone) 10 is connected to a GW (Gate Way) unit 13 via a mobile communication network 11 which is a cellular telephone network. The GW unit 13 is connected to an Internet 12. The Internet 12 accepts a plurality of content servers 14 storing content data of various data formats such as characters and images, and it is possible to identify the content servers 14 with addresses which are individually given to the content servers 14.
In this mobile communication system, an access request from the mobile user terminal 10 to the content server 14 is transmitted to the GW unit 13 via the mobile communication network 11. With the mobile user terminal 10, the access request is given so as to designate an address for identifying the content server 14 in the Internet 12. The GW unit 13 executes a protocol conversion and a like between the mobile communication network 11 and the Internet 12 and transmits the access request to the content server 14 via the Internet 12. The content server 14 takes designated content data from various previously stored content data in accordance with the received access request and transmits the designated content data to the GW unit 13 via the Internet 12. The GW unit 13 executes the protocol conversion and a like and transmits the designated content data via the mobile communication network 11 to the mobile user terminal 10 which requires to obtain content data. The mobile user terminal 10, for example, displays the content data including image data on a display screen in accordance with a data format of the received content data.
Now, concerning the mobile communication network 11 in the conventional mobile communication system shown in FIG. 7, generally, a mobile communication service area includes a plurality of small areas, a radio communication base station 15 is located in each small area, and thereby a wide service area such as a cellular telephone network is carried out. When the mobile user terminal 10 moves from the radio communication base station 15 area to an adjacent area, the mobile user terminal 10 keeps a communication connection with another terminal by roaming service between the radio communication base stations 15 without disconnection. Generally, the “roaming service” is a meaning that a mobile user terminal 10 communicates in an area of a common carrier with which no contract is made, however, hereafter, the roaming service includes that information necessary for communication is received and transmitted regardless of a contract.
When the mobile user terminal 10 issues an access request to the content server 14, the mobile user terminal 10 exists in an area of the radio communication base station 15 which manages a first area in the mobile communication network 11. Then, when it is assumed that the mobile user terminal 10 moves from the first area to a second area by movement 16, the mobile user terminal 10 is connected to a radio communication base station 17 which manages the second area in the mobile communication network 11 by the execution of the roaming service. At this time, roaming information as communication information necessary for communication with the content server 14 is transferred from the radio communication base station 15 managing the first area to the radio communication base station 17 managing the second area. Therefore, it is possible for the mobile user terminal 10 to keep the communication connection with the content server 14 via the GW unit 13 by the execution of the roaming service.
As described above, in the conventional communication system, though the roaming service between radio communication base stations 15, 17 in the mobile communication network 11 is executed, connection of the GW unit 13 is kept in a case in that the mobile user terminal 10 receives content services from the content server 14. Therefore, though the mobile user terminal 10 moves geographically between two places at a long distance, a service is executed via the GW unit 13 first accessed.
However, a moving time is shorten by advances of locomotion, a case increases in that content services are provided while connecting with the mobile communication network 11 having a very wide area. In this case, when the mobile user terminal 10 connects with the GW unit 13 first accessed, a long distance communication is executed by the roaming service in the mobile communication network 11. When a network becomes large and a number of mobile user terminals 10 increases, a frequency of long distance communications for connection with the GW unit 13 in the mobile communication network 11 increases. Therefore, there are problems in that a throughput of the mobile communication network 11 deteriorates and a communication cost of the mobile user terminal 10 increases.
Also, though a plurality of GW units 13 are provided by increment of content service users, in a case that the mobile user terminal 10 moves and connects with a GW unit 13 which is firstly accessed, there are problems in that use efficiency of the GW unit 13 lowers and it is impossible to provide stable services.